One other thing to be aware of is that the Crucial firmware updater (standalone boot) only recognizes the standard four ports. You cannot flash drives connected to add-on controllers, even if they are bootable.
The MX200 is now at MU02, but still shipped with MU01 a month ago.
Actually AKAIK, that's an issue with any make of 2.5" SSD. Here's a post of mine from over two years ago related to the Samsung SSD and Apricorn x2:
https://forums.macrumors.com/threads/samsung-ssd-firmware-with-an-apricorn-velocity-x2-card.1615759/
Lou